Catalytic cracking of shale oil over zeolite catalyst

ABSTRACT

A PROCESS FOR CATALYTICALLY CRACKING OF OILS DERIVED FROM OIL SHALE WHICH CONTAIN HIGH AMOUNTS OF NITROGEN, I.E., OVER ABOUT 1 PERCENT IS DISCLOSED. THE CATALYTIC CRACKING IS CONDUCTED AT TEMPERATURES OF ABOUT 975* F. UP TO ABOUT 1200* F. AT THESE TEMPERATURES THE ADVERSE EFFECTS OF NITROGEN POISONING OF THE CATALYST ARE SUBSTANTIALLY NEGATED.

3,654,141 Patented Apr. 4, 1972 United States Patent 01 hoe v 3,654,141 --CATALYTIC CRACKING OF SHALE OIL OVER ZEOLITE CATALYST p Harrison C. Maryland, Lockpor t, Ill., assignor to Atlantic Richfield Company, New York, NY.

No Drawing. Filed Jan. 8, 1969, Ser. No. 789,937

' Int. 01. 010g 11/02, 11/18 U.S. (:1. 208-120 s Claims ABSTRACT OF THE DISCLOSURE A process for catalytically cracking of oils derived from oil shale which contain high amounts of nitrogen, 1.e., over about 1 percent is disclosed. The catalytic cracking is conducted at temperatures of about 975 F. up to about 1200 F. At these temperatures the adverse effects of nitrogen poisoning of the catalyst are substantially negated.

The free world reserve of mineral oil is limited and, as a result, great attention has been focused on the recovery of mineral oil from oil shale. There are great differences in structure and composition between the petroleum oils, such as Mid-continent oils, and oils derived from oil shale. One of these compositional differences is the amount of nitrogen in the oil. Most petroleum gas oils contain a maximum of about 0.05 weight percent nitrogen. However, shale oils, and even some gas-oils which have not been treated for nitrogen removal, or at least not effectively so, generally contain nitrogen in an amount of 1 to 2 Weight percent or'higher. This nitrogen content has led to problems in the catalytic cracking of normally liquid oils prepared from shale oil. When these oils are catalytically cracked at the range of conditions ordinarily used for cracking petroleum oils or denitrogenated shale oils, poor results are obtained because of nitrogen poisoning of the catalyst. More severe operating conditions are required as compared with those needed for cracking feedstocks of similar boiling range and hydrocarbon types but with lower nitrogen content. Also, inferior product distributions, i.e., less gasoline and other liquid products boiling below the feedstock, are obtained.

This difliculty of nitrogen poisoning of the catalyst is believed to be caused by the tendency of the nitrogen compounds in the feed to be preferentially adsorbed on the acidic sites on the catalyst. Since these acidic sites are the primary source of catalytic activity of the catalyst, the blocking of a substantial number of acidic sites substantially reduces the activity of the catalyst. The substan tial blocking of these acidic sites along with the more severe operating conditions required for the high nitrogen feedstocks lead to high yields of undesired products such as coke and gas.

It has now been found that if the catalytic cracking of oils prepared from oil shale is carried out at temperatures of about 975 F. or higher, up to a maximum tem perature of about 1200 F., preferably about 1000 to 1100 F., the adverse efiects of high nitrogen content are materially negated. Temperatures above about 1200 F. are unsuitable for use in conventional catalytic cracking equipment, and such higher temperatures would require the development of special reactor systems to handle very high space velocities and quick heating and quench systems. The preferential adsorption of nitrogen is apparently reduced by the use of high catalytic cracking temperatures, i.e., about 975 F. to about 1200 F.

Catalytic cracking temperatures of above 975 F. (i.e. to about 1200 F.) have been proposed before the Midcontinent oils, as shown, for example, in U.S. Pats. 3,140,249 and 3,140,251, but these oils are not high nitrogen-containing oils as explained above and their use does not raise the problem ofsevere nitrogen poisoning. Thus,

- the invention of the instant application is designed to catalytically crack high nitrogen shale-oilfeedstocksto obtain gasoline as aprincipal-p'roduct. These oils prepared from oil shale contain at least about 1 or2-percent nitrogen or higher and, in the case of gas oils, boil primarily in the range of about 500 to about 1000 F. or even about 650 to about 900 F. Other high nitrogencontaining, normally liquid shale oils boiling above the gasoline range, even residuals, can be cracked by the method of this invention.

Solid oxide catalysts, both naturally-occurring, activated clays and synthetically prepared gel catalysts, as well as mixtures of the two types, have long been recognized as useful in catalytically promoting conversion of hydrocarbons. A popular natural catalyst is acidactivated montrnorillionite. For cracking processes, the solid oxide catalysts which have received the widest acceptance today are usually activated or calcined predominantly silica or silica based, e.g. silica alumina, silica magnesia, silica zirconia, crystalline aluminosilicate, etc., compositions in a state of slight hydration and containing small amounts of acidic oxide promoters in many instances. Popular synthetic gel cracking catalysts generally contain silica and about 10 to 30% alumina. Two such catalysts are Aerocat which contains about 13% A1 0 and High Alumina Nalcat which contains about 25% A1 0 with substantially the balance being silica. The catalyst may be only partially of synthetic material; for example, it may be made by the precipitation of silica-alumina on clay, such as kaolinite or halloysite. One such semi-synthetic catalyst contains about equal amounts of silica-alumina gel and clay.

Among the preferred catalysts which can be used in the present invention are those containing a catalyticallyeffective amount of a crystalline aluminosilicate. These materials are known in both naturally-occurring and synthetic forms. Those which have been found advantageous for use as catalysts for cracking hydrocarbons are often characterized by relatively uniform pore size in the range of about 8 to 15 A., preferably about 10 to 14 A., and a silica-to-alumina mole ratio ranging from about 2 to 12:1, preferably about 2 or even 4 to 6:1. The sodium ions occurring in the generally available forms poison the catalytic activity of crystalline aluminosilicates and can be removed by ion exchange and replaced by hydrogen, hydrogen precursors such as NH or va cation of a metal from Group I-B to Group VIII, inclusive, of the Periodic Table. Frequently the sodium is replaced by a combination of hydrogen or a hydrogen precursor and a metal or a combination of metals, e.g. about 15 to 60% of the exchanged ions being hydrogen or a hydrogen precursor. The metals most often utilized are the rare earth metals, especially cerium, or a mixture of rare earth metals such as cerium and lanthanum. Because of the expense and difiiculty in controlling the activity of the ion-exchanged crystalline aluminosilicates, these materials are rarely used alone Usually such materials are combined with refractory inorganic oxide matrix, such as naturally occurring clays, and the like, and/ or synthetic gels, such as alumina, silica-alumina, and the like. Materials suited for use as the inorganic oxide matrix are well-known to the art and are most often oxides of the metals of Groups I'I to VI, especially 111 and IV, of the Periodic Table, preferably containing about 55 to silica by Weight. The crystalline alumino-silicate is generally from about 5 to weight percent of the mixed catalysts, although amounts less than about 50 percent, e.g. about 10 to 30 percent, are often preferred from an economic standpoint.

The physical form of the catalyst varies with the type of manipulative process to which it will be exposed. In

fluid-catalytic processesgase's are used-to-convey the catalyst in the form of a fine powder, generally in a size range of about 20 to 150 microns. In the TCC or .Thermofor process the catalyst-is in the form of beads which are conveyed-by elevators or by gas streams. Gen erally. these. beads-:may range in size up to about /2 diameter. When fresh, the minimum sized bead is generally about Mi". Other types of processes use other forms of catalyst such as tablets 'or extruded pellets. The cracking process of this invention preferably uses the fluidized solids technique.

A test was made in a laboratory catalytic cracking unit which contained a small fluidized bed reactor with provisions for continuously feeding oil and the catalyst, the oil being a 625 to 925 F. boiling range distillate shale oil (without hydrogenation) containing 2.2 weight percent nitrogen. The cracking temperature was 1000 E, the shale oil feed rate was Weight units per hour per weight unit of catalyst in the reactor hot zone, i.e., 5 WHSV, and the catalyst was fed at the rate of 16 weight units per hour per weight unit of shale oil, i.e., a 16 to 1 catalystto-oil ratio. The catalyst used was a rare-earth (including cerium) exchanged crystalline aluminosilicate containing catalyst, containing about 0.5 to 0.9 weight percent Na, calculated as the free metal, about 0.6 weight percent rare-earth, calculated as the free metal, a silica to alumina mole ratio of about 4.5 to 1, a pore radius of about 13 angstroms, and containing about percent crystalline aluminosilicate mixed with an amorphous SE -A1 0 cracking base, part of which is derived from clay. The product distribution showed about 11 Weight percent coke on the feed and substantial yields of 430 F. E.P. gasoline and 430-'6()0 F. distillate cuts. The 600 F. plus cut contained 4 p.p.m. Ni, 6 p.p.m. V and 1 p.p.m. Fe which is satisfactory for most purposes. The gasoline contained 0.85 weight percent nitrogen and the 430- 600 F. cut contained 1.43 weight percent nitrogen. These nitrogen levels indicate that the gasoline could be improved by denitrogenation by hydrogen treatment and then catalytic reforming to increase its octane rating.

It is claimed:

1. In a process for the catalytic cracking of normally 4 liquid shale oil'containing at least one" weighhprcent shale oil derived nitrogen and boiling above the gasoline range, said cracking being in the presence of a silica catalyst, the improvement which comprises conducting said catalytic cracking at a temperature of from about 975 F. to about'1200 F. and with a catalyst containing a catalytically etfective amount of crystalline aluminosilicate having a'pore size of about '8 to 15A. and "a silica-to-alumina mole ratio of fromabout 2:1 to12: 1.

2. The process of claim. 1 wherein the crystalline aluminosilicate has a silica-to-alumina mole ratio of from about 4:1 to 6:1.

3. The process of claim'z'wherein the cracking is conducted at a temperature offrom about 1000 F. to about 1100 F. p

4. The process of claim 2 wherein the catalyst contains about 10 weight'percentto 30 weight percent of .a rare earth exchanged crystalline aluminosilicate 5. The process of claim 4 wherein the temperature is from about 1000 F. to about 1100 t i 6. The process of claim 5 wherein the rare earth is cerium.

7. The process of claim .6 wherein the crystalline aluminosilicate pore size is from about 10 to 14 A. p

8. The process of claim 7, whereinthe catalyst has an amorphous silica-alumina base.

References Cited I I, UNITED STATES PATENTS. I v

5/1968 Buss l 208 -111 DELBERT E. GANTZ, Primary Examiner 'G. E. SCHM ITKONS, Assistant Examiner US. 01. X.R. 20s' 11; 2s2 s z 

